This invention relates to tubular materials; more particularly, this invention relates to a process for the solid phase deformation of tubular materials of an orientable, thermoplastic polymer and to the oriented tubular materials so produced.
In our patent GB No. 2060469B we have described a process for the solid phase deformation of a workpiece of an orientable, thermoplastic polymer, which process comprises providing the workpiece of the essentially unoriented polymer at the entry side of a die; applying to the workpiece from the exit side of the die a draw tension insufficient to cause tensile failure of the workpiece; and drawing the workpiece through the die so that its plastic strain is progressively increased during start-up of the process.
This invention seeks to provide oriented tubular materials having improved mechanical properties, especially in directions other than the machine direction.